At the time I am writing this it is too easy to make a fake account and write fake reviews on google business listings. I have negative defamatory fake reviews for my company. As far as I can tell they violate google's own policies but there is no way to remove them because they didn't write anything. Its just stars.
On the other hand I know of competitors who boast about having fake reviews of the same nature but positive ones they have made.
This is the issue. Google needs to create a minimum text requirement of at least a couple sentences to help remove fake reviews. This would make reviews, both positive and negative, easier to flag.